It is well known in the art to provide acoustical and thermal insulators on an automobile, truck or other vehicle in an effort to protect and insulate the operating or passenger compartment from the noise and heat generated by the mechanical equipment of the associated vehicle. Toward this end, mats of high temperature glass fibers have been utilized, eg. (a) on the fire wall between the dashboard and engine compartment and (b) along the floor pan of the vehicle between the passenger compartment and the drive line and exhaust system. These materials provide heat insulation which makes it possible to maintain cooler and more comfortable temperatures in the operator/passenger compartment particularly during the summer months. Additionally, these materials provide needed sound insulation, reducing or eliminating various mechanical sounds of the motor, drive train as well as the suspension and tires as the vehicle travels over the often rough and bumpy surface of the roadway.
Prior art examples of heat and sound insulating materials, mats and panels are found in a number of patents including U.S. Pat. No. 4,948,660 to Rias et al., U.S. Pat. No. 5,283,111 to Schlecker and U.S. Pat. No. 5,633,064 to Ragland et al.
The Rias et al. patent discloses a heat and sound insulating panel including an outer paint coating, a sheet of glass fibers, an aluminum film, a heat sealing film of polyethylene and an insulating mineral fiber layer mat. In the Schlecker patent, a multi-layered composite is disclosed including a woven polyethylene/polypropylene mat, a reflective layer of aluminized polyester or polypropylene and an insulating layer of non-woven batt of insulating textile fibers including glass. The insulating layer may include a scrim of polyester with the fibers of the batt needle punched into the scrim.
In both the Rias et al. and Schlecker references, the heat reflective foil is provided as an interior layer rather than an outer layer of the insulator or panel. This allows heat to build up in at least the outer layers of the insulator or panel between the metallic film and the heat source. This adsorption of heat limits construction material selection to relatively high melting point materials and reduces cooling efficiency of the surrounding mechanical components. Over time this allows a greater transfer of heat into the operator/passenger compartment of the vehicle.
In the Ragland et al. reference, a heat barrier laminate is provided having a metal layer adhesively bonded on one side to an insulating layer and on the other side to a flame retardant layer. A second metal layer is bonded to the other side of the insulating layer. While such an insulator provides very good thermal insulation, it does not provide the best acoustical insulation. Further, while good thermal insulation is provided, the use of two metallic foil layers adds significantly to the cost of manufacturing the insulator or panel. The two foil layers also tend to trap heat between the layers by reflecting heat back and forth. This can limit the selection of materials for the insulating layer to those with higher melting points. For certain applications this may eliminate one from possibly using a material with more desirable acoustical and/or thermal insulating properties. Accordingly, a need is identified for an improved insulator or panel providing superior acoustical and thermal insulation properties at a reduced overall manufacturing cost.